TCR evolution and energy transport in the magnetotail

Travelling compression regions (TCRs) appear in the Earth`s magnetotail as regions of compressed magnetic field lines travelling towards the Earth and down the tail. They are observed during magnetic substorms - strong disturbances in the Earth`s magnetosphere which can damage satellites, affect radio and GPS signal propagation and destroy electrical power systems. Due to the significant threat from space weather phenomena on our society, a better understanding of substorm-related processes and, in particular, the mechanism of geoeffective energy transport in the tail is of tremendous scientific and societal importance. This project is aimed towards answering the following open questions: (1) How do TCRs and their drivers (e.g., plasmoids) evolve in time? (2) What is the physics of the transport of compressed and reconnected magnetic field lines in the Earth`s magnetotail and how big is this transported magnetic energy compared to the thermal and kinetic energy of the plasma inside the plasmoid? (3) How can we describe TCRs and plasmoids self-consistently in terms of both their magnetic field and plasma properties? (4) Why are there differences in the earthward ("BBF- like") and tailward ("plasmoid-like") evolution of TCRs? To answer these questions we will use observations, a theoretical model and a numerical simulation. THEMIS, as well as the subsequent mission ARTEMIS, represent an outstanding opportunity to investigate the evolution of TCRs and plasmoids due to the spatial separation of probes P1 and P2 of about 10 RE during 2008 and 2009 at 20-30 RE downtail and ~1000s of km to 20 RE in 2010 and 2011 at 55-65 RE downtail. Additionally, the unique tetrahedron spacecraft constellation of the long lasting and highly successful Cluster mission can be utilized for multi-satellite probing of the TCR and the associated plasma bulge when Cluster is in the tail, at distances 12-20 RE. We will extend our incompressible plasma model for the compressible fluid case to describe the energy redistribution due to magnetic reconnection. Based on this model we will be able to fit TCRs globally and describe the entire energy transport in terms of magnetic, kinetic and thermal energy. Finally, we will use an already developed numerical MHD simulation to investigate the evolution of TCRs and the energy transportation in order to guide the theoretical work - which is based on idealized configurations, - and extend the single point spacecraft observations into a coherent large scale model. By using theoretical, observational and numerical methods we will thus achieve deeper insight into the evolution of TCRs and the internal structure of plasmoids and provide comprehensive physical understanding of magnetic and plasma energy transport in the Earth`s magnetotail.